MEMS or Micro Electro Mechanical Systems have become useful in a variety of fields. These systems have been applied to such technologies as inkjet printers, accelerometers, microphones, optical switching, and fluid acceleration. Over the last decade, there has been a focus towards the development of a subclass of these devices, termed Micro-Opto-Electro-Mechanical Systems (MOEMS).
One type of MOEMS device is an electrostatically deflectable membrane. Such MOEMS membranes are used in a spectrum of optical applications. For example, they can be coated to be reflective and then paired with a stationary mirror to form a tunable Fabry-Perot (FP) cavity/filter. They can also be used as stand-alone reflective components to define the end of a laser cavity, for example.
Typically, a voltage is applied between the membrane and an adjacent structure. When paired with a second fixed reflector, the FP cavity's separation distance changes through electrostatic attraction as a function of the applied voltage.
There are a few main components that typically makeup a MOEMS membrane device. In one example, the MOEMS membrane device includes a handle wafer support structure. An optical membrane or device layer is added to the handle wafer support structure; a deflectable membrane structure is then fabricated in this layer. This MOEMS membrane device includes an insulating layer separating the wafer support structure from the membrane layer. This insulating layer is subsequently partially etched away or otherwise removed to produce the suspended membrane structure in a release process. The insulating layer thickness defines an electrical cavity across which electrical fields are established that are used to electrostatically deflect the membrane structure.